I believe that some models of the Shackleton had 20mm cannon in the nose as well.
That was the MR3 F10, tricycle undercarriage and tip tanks, a very attractive but also a quite dangerous aircraft I believe, with rather vicious stall characteristics, due the the considerable increase in all up weight.
An old neighbour of mine flew MR2's and 3's, he said the MR2 had very good flight characteristics, but every crews worst nightmare was hitting a big still air pocket in an MR3, if one of the wings stalled, it was all over, no chance of recovery... He hated them.